The most recent World Series Champions– the Kansas City Royals for those living under a rock, won on the strength of their bullpen, led by bullpen ace Wade Davis. Davis has become a household name especially in the playoffs the past few seasons where he has been virtually un-hittable. Earlier this season, I debuted a metric that I dubbed RWAR, which measures the impact of relief pitchers and quantifies that impact on a WAR based scale. Unsurprisingly, Davis found himself near the top of the list in 2015 after being near the top in 2014 as well. Using the RWAR data for 2015 and seasons prior, I will be attempting to draw a number of conclusions trying to identify underused or even misused relievers who could thrive in the bullpen ace role.
Bullpen Ace: A term used to describe the best reliever on a particular team. Often times described as the closer, but in an ideal world would be the pitcher used in the most important late-inning situation of the game.
In my first attempt to find pitchers that fit this description, I used the Z-scores of several different metrics to develop a score for each pitcher. Click here for an explanation of Z-score. The six metrics I chose were K/9, BB/9, HR/9, GB%, Contact%, and SwStr%. These all were chosen because these were six of the metrics that I felt were most likely to be important for relievers. K/9, GB%, Contact%, and SwStr% are all indicative of an ability to get out of potential jams, whether through a strikeout or through a double play. The other two metrics are important because they show an ability to minimize the number of baserunners (BB/9) and the ability to avoid one big swing to lose the game (HR/9).
This early and very crude attempt proved to be more successful than expected as the correlation between the sum of the Z-scores explained about 50% of the variation in RWAR. When looking at the highest-rated relievers by Z-score, one name in particular stood out, Carter Capps.
Capps only threw 30 innings this season due to an arm injury that cost him the end of his season, but prior to that Capps was downright un-hittable. He had an absurd SwStr% of 25%, which could be driving up his value on this ranking and will likely regress in 2016, but all around each one of the six metrics Capps was above average in 2015. However, Capps does not have a direct path to a closers’ role and A.J. Ramos, who closed for the Miami Marlins last season performed well in the role. Nevertheless, Capps and Ramos have the potential to turn the Marlins’ bullpen into a weapon as Ramos ranked 12th on the list just behind Craig Kimbrel.
This was just a first attempt at trying to find guys who could excel in a key late-inning role as each of the six metrics are weighted equally. In future attempts it will be interesting to see if high strikeout guys will perform better than groundball specialists as is the consensus around the game. Keep looking back over the next few weeks in order to find other names to watch in 2016.